Stems are known for handlebars of bicycles and the like that comprise a support, generally tubular, provided with adjustable joining means to the steering fork and to the bar of the handlebar, in order to allow the user to adjust the handlebar, such as height, inclination, etc.
Some of the stems of the known type, such as described in U.S. Pat. No. 5,687,616, comprise, for instance, ample openings realized in the support of the same stem to allow the adjustable connection to the bar of the handlebar, but also, in some cases, with the steering fork.
Such openings define two opposed pipe portions that, opportunely shaped, realize a sort of clamp that is, for instance, shut around the bar of the handlebar with a bolt or with other equivalent removable means.
When the user makes an adjustment, for instance to vary the inclination of the handlebar to get a more comfortable position, the user must first loosen the bolt to unclamp the pip portions, adjust the handlebar to the desired position, and then tighten the bolt to secure the handlebar against the pipe portions.
The deformation to which the pipe portions of the support are submitted to shut the bar of the handlebar and the repeated operations of opening and tightening to make the handlebar adjustments can cause concentrate stress at both the handlebar and the pipe portions.
Such stress concentration, due also to the fact that the area of contact between the stem and the bar of the handlebar is rather limited, may cause breakings around the openings, mechanical clearances and other undesirable phenomena due to the mechanical stress concentrated in such critical zones.
In addition, the adjustment of the angular position of the bar of the handlebar is not easy or comfortable because it requires the manipulation of elastically deformable metallic parts.
These difficulties are still more evident when it is necessary to completely replace the bar of the handlebar, and not just to simply adjust its position.